Studio_Macuga

Hi everyone! Long time lurker, first time poster. I'm having some trouble with my Liyu SC1261 - I've been using the pen function for drawing technical imagery and in the last few runs, the plotter has been fading out in the centre 50cm or so of the bed (see attached images for examples). I initially thought this might be an issue with the biros I was using however this has proven to not be the case as I have tried different pens from various manufacturers and all are doing the same thing - I have tried upping the pen pressure to the max but this has also done nothing. I know this plotter has been around for a fair few years so I'm wondering if this issue is specifically with the carriage belt tension? The plotter is well maintained - cleaned on a regular basis and stored away from harm etc., so I'm pretty positive there isn't some kind of jam in the main rollers. I've also tried seeing if placement of the pinch rollers is helpful in aiding the change in pressure but sadly this is not the case. Does anyone have an idea of what this might be caused by and the first step I can take in solving the issue? Thanks so much in advance and have a lovely day! - Melissa x